Imidazopyrrolone dicarboxylic acids and a process for their preparation



Oct. 21, 1969 MUNEH|KO suzu ET Al. 3,474,109

IMIDAZOPYRROLONE DICARBOXYLIC ACIDS AND A PROCESS FOR THEIR PREPARATIONFiled Dec. 29, 1966 Fla Wave/engfh M E H m 0 9 A W F m m m 0 u m w W W xWavenumber (cm") 1% gfimmtu cmuxml 0 0 w M E H 0 U 0 0 U 9 )w 0 h 0 W5 WW 9 W Wavenumber (cm' INVENTORS warm/4o muuf United States Patent3,474,109 IMIDAZOPYRROLONE DICARBOXYLIC ACIDS AND A PROCESS FOR THEIRPREPARATION A Munehiko Suzuki, Yokosuka-shi, Etsuo Hosokawa, Yokohama,and Shinsuke Hirata and Tetsuo Hoshino, Kawasaki-shi, Japan, assignorsto Showa Electric Wire and Cable Co., Ltd., Kawasaki-'shi, Japan, acorporation of Japan Filed Dec. 29, 1966, Ser. No. 605,761 1 Claimspriority, appliczllt/ionv Japan, Jan. 8, 1966,

4 Int. Cl. C07d 57/00 US. Cl. 260-3092 10 Claims ome The process forpreparing the compounds is that diaminomonocarboxylie acids are reactedwith tricarboxylic acid anhydrides; tetra-amino compound (1 mole) isreacted with tricarboxylic anhydride (2 moles); diamino-monocarboxylicacid (2 moles) is reacted with tetracarboxylic dianhydride ('1 mole).

BACKGROUND OF THE INVENTION This invention relates to a novel class ofimidazopyrrolone dicarboxylic acids which are useful for the productionof various synthetic resins with improved thermal stability and areuseful as cross-linking agents for epoxide and other synthetic resins,and to a process for the production thereof.

In the field of electric insulation employing synthetic resins or in thefield of cross-linking agent for synthetic resins, there has been anintensive effort to find out the means for improving thermal stabilityof such resins or to develop new polymers with improved thermalstability.

As a result of this effort, various new classes of synthetic resinshaving improved thermal stability have been discovered, includingpolyimide resin, which is obtained by reacting tetracarboxylicdianhydride with diamine in an organic polar solvent,polyimidazopyrrolone resin, which is described in NASA TN D-3 1-48 andis obtained by reacting tetracarboxylic dianhydride with 3,474,109Patented Oct. 21, 1969 tetramine in an organic polar solvent, and thelike. However, no satisfactory results have been obtained in the fieldsof polyester resin, polyamide resin or epoxide resin. Accordingly, it isa principal object of this invention to provide a novel class ofimidazopyrrolone dicarboxylic acids which are useful for the productionof polyester or polyamide resins with improved thermal stability and areuseful as cross linking agent for epoxide resins. Another object of thisinvention is to provide a method for preparing such a novelimidazopyrrolone dicarboxylic acid. Other objects and advantages of thisinvention will be apparent from the following description and claims.

BRIEF EXPLANATION OF THE DRAWINGS Attached drawings, FIGS. 1-3, are theinfra-red absorption spectra of the present imidazopyrrolonedicarboxylic acids prepared in Examples 1-3, respectively.

SUMMARY OF THE INVENTION The imidazopyrrolone dicarboxylic acids of thepresent invention are shown by the general formula:

wherein each of R and R is a trivalent radical having at least twocarbon atoms and is a member selected from the group consisting ofaliphatic, aromatic and heterocyclic radicals, and in case ofheterocyclic, one of R and R may contain imidazopyrrolone ring, the samecarbon atom or two adjacent of substantially adjacent carbon atoms ofsaid trivalent radical being bonded through single links to the twonitrogen or two carbon atoms of the above formula, thereby forming animidazopyrrolone nucleus. As stated previously, the presentimidazopyrrolone dicarboxylic acids may contain imidazopyrrolone ring ineither R or R which may be rep resented by the following sub-generalFormulae A and A wherein R is a trivalent radical having at least twocarbon atoms and is a member selected from the group consisting ofaliphatic, aromatic and heterocyclic radicals, the same carbon atom ortwo adjacent or substantially adjacent carbon atoms of the trivalentradical being bonded through single links to the two nitrogen or carbonatoms of the above formulae, and R is a tetravalent radical having atleast two carbon atoms and is a member selected from the groupconsisting of aliphatic, aromatic, and heterocyclic radicals, in eachside of the R the same carbon atom or two adjacent or substantiallyadjacent carbon atoms of the tetravalent radical being bonded throughsingle links to the two nitrogen or carbon atoms of the above formula,thereby forming a pair of imidazopyrrolone nuclei, in either case.

The imidazopyrrolone dicarboxylic acids represented by the Formula A arein general prepared by the following reaction Formula B.

Likewise, the imidazopyrrolone dicarboxylic acids represented by theFormulae A and A are prepared by the following reaction Formulae B and Brespectively.

In these formulae, R in the tetra-amine or tetra-carboxylic dianhydride,R and R in the diamine monocarboxylic acid or tricarboxylic acidanhydride, and R are preferably selected from the group consisting of Q(I) @Q wherein X is C, N, Si, P, S or 0.

The following members are also included in these radicals:

U (l (j l N o s U l./ F

and

A pair of amino radicals or carbonyl radicals are bonded through singlelinks to the same carbon atom or two adjacent carbon atoms of one ofthese radicals. However, these radicals may be attached to twosubstantially adjacent carbon atoms as in the case of naphthalene 1,2 ornaphthalene 5,6. The tetra-amine compounds adapted for use in thepractice of this invention may include 3,3- diarninobenzidine, 1,2,4,5tetra-aminobenzene, 3,3',4,4'- tetra-aminodiphenylsulfide,3,3',4,4-tetra amino-diphenyl methane, 3,3',4,4-tetra-arnino-diphenylketone and the like. Typical examples of tricarboxylic acid anhydridemay include trimellitic anhydride, 3,4,4-diphenyl ether tri-carboxylicacid anhydride, and ethylene tricarboxylic acid annydride. Examples ofdiamino monocarlboxylic acids may include 2,3-diamino-benzic acid,3,4-diaminobenzoic acid, 5,6 diamin0-3-nicotic acid, 2,3-diamino-2-naphthoic acid, and 3,4-diamino-hydro-cinnamic acid.

As for the tetracarboxylic dianhydride employed in the practice of thepresent invention, there include pyromellitic dianhydride, 2,3,6,7naphthalene tetracarboxylic dianhydride, 3,3',4,4diphenyl-tetracarboxylic dianhydride, 3,3',4,4 benzophenonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxypheny1) propanedianhydride, 1,2,3,4 cyclopentane tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl) sulfone dianhydride, perillene-3,4,9,l0-tetracarboxylic dianhydride, bis (3,4 dicarboxyphenyl) etherdianhydride, and ethylene tetracarboxylic dianhydride. In thepreparation of imidazopyrrolone dicarboxylic acid according to thisinvention, thorough attention should be paid to the precise control ofemploying amounts of each reaction ingredient, and of temperatureelevating rate, since each of these factors has a great influence on theyield of imidazopyrrolone dicarboxylic acid.

For example, when a larger excess amount of tetraamine is reacted withtricarboxylic anhydride, the following Compound C will be obtained as amain product.

On the other hand, if a larger excess amount tricarboxylic anhydride isreacted with tetraarnine, the following Compound C will obtain as a mainproduct.

The formation of imidazopyrrolone dicarboxylic acid in the presentmethod, in general, occurs in two steps as shown, for example, below inthe reaction Formulae D However, especially in the case of employing nosolvent, too rapid elevation of reaction temperature will cause such as(C and (C Therefore, it is desirable to employ saoichiometric amounts ofreagents or adequately controlled amounts of reagent (i.e. one reagentbeing at most in 25% excess of the stoichiometric amount thereof), andto employ an appropriate temperature elevating rate (e.g. in case ofemplaying no solvent, the preferable range being 25 C. per minute).

In a preferred embodiment of the present method employing no solvent,approximately stoichiometric amounts of reagents are placed in areaction vessel equipped with mechanical stirrer, and while stirring andintroducing inert gas (e.g. nitrogen gas) therein, the reaction mixtureis gradually heated up to 140-250 C. with the care that the temperatureof the mixture is elevated at a rate of 2- 5 C. per minute. Thereafter,the introduction of inert gas is stopped and the mixture is furtherheated at 200- 300 C. under a vacuum of about 0.1 mm. Hg, for asufficient time to complete the inter-molecular condensation reaction.In another embodiment of the present method employing a solvent,approximately stoichiometric amounts of reagents are dissolved in aninorganic or organic solvent and thus prepared solution is, whileintroducing or not introducing inert gas therein, refluxed for 2-10hours to complete the reaction. In this case, various solvents having noharmful effect on the reaction may successfully be employed and typicalexamples of such solvenst may include glacial acetic acid, phenol,cresol, xyle nol, pyridine, dimethyl acetamide, dimethyl formamide,N-methyl-2-pyrrolidone, polyphosphoric acid and the like.

Thus prepared imidazopyrrolone dicarboxylic acids are in general hardsoluble in water and in organic solvents, and are characterized byhaving an excellent thermal stability and having considerably highermelting point of more than 300 C. The present imidazopyrrolonedicarboxylic acids are very useful as the raw materials of polyester andpolyamide resins and as the cross-linking agents for expoxide and othersynthetic resins. Examples of the invention:

Further details can be seen from the following examples which are givensolely for the purpose of illustration and are not to be construed aslimitations of this invention. Unless otherwise stated, the partstherein are by weight.

Example 1 1.92 parts of trimellitic anhydride and 1.15 parts of3,3',4,4'-tetra-amino-diphenylether were placed in a threeneck flaskequipped with stirrer and thermometer and the mixture was, undernitrogen streams, heated up to 150 C. with a temperature elevating rateof 2 C. minute. During said heating, the mixture began to melt and theformation of water was observed.

After stopping the nitrogen supply, the mixture was further heated at200 C. under 0.1 mm. Hg, for 2 hours. Thus obtained reaction mixture wasdissolved in 50 parts, of dimethyl sulfoxide and the solution was pouredinto 50% ethanol aqueous solution to precipitate yellow reactionproduct. Analytical data showed that this product was theimidazopyrrolone dicarboxylic acid of the structural formula:

C=N =0 (2 0 N II II o HOOC- COOH Melting point: 314316 C.

Elementary analysis.-Calculated (as C H O ,N C, 66.42%; H, 2.58%; N,10.33%. Found: C, 66.32%; H, 2.65%; N, 10.21%. Infra-red absorptionspectrum: (shown in FIG. 1).

Example 2 1.92 parts of trimellitic anhydride and 1.14 parts of 3,3',4,4-tetra-aminodiphenyl methane were reacted as described in Example1 and yellow precipitated product was obtained.

Melting point of this product was 280282 C. and elementary analysis datawas as follows. Calculated as (C I-I O N C, 68.89%; H, 2.96%; N, 10.37%.Found: C, 68.87%; H, 3.12%; N, 10.54%. Infra-red absorption specrtum wasshown in FIG. 2. Analytical data indicated that this product was theimidazopyrrolone dicarboxylic acid of the formula:

HOOC C=N v N=C- COOH i C N CH N 0 t, .1

Example 3 1.92 parts of trimellitic anhydride, 1.07 parts of 3,3-diaminobenzidine and 50 parts of pyridine were placed in a reactionvessel equipped with mechanical stirrer, condenser, and thermometer, andthe mixture was, while stirring and introducing nitrogen stream, heatedat the reflux temperature of pyridine (i.e. 115 C.) for 10 hours.

Precipitated yellow product was separated, washed with ethylether anddried.

Elementary analysis-Calculated (as C H O N C, 68.44%; H, 2.66%; N,10.64%. Found: C, 68.47%; H, 2.74%; N, 10.65%. Infra-red absorptionspectrum: (shown in FIG. 3). Analytical data showed that the compoundwas the imidazopyrrolone dicarboxylic acid of the formula HOOC O=NExample 4 Employing the same procedure as described in Example 3, 1.55parts of trimellitic acid anhydride and 1.80 parts of3,4-diaminohydrocinnamie acid were reacted in the presence of 50 partsof 116% polyphosphoric acid at 200 C. for 2 hours.

Subsequently, the resulting reaction product was poured into a 50:50water-ethanol solution, precipitated and separated.

Thus prepared compound was found to be the imidazopyrrolone dicarboxylicacid of the formula:

N7C- COOH mmmga Elementary analysis.Calculated (as C H O N C, 64.29%; H,3.57%; N, 8.33%. Found: C, 64.50%; H, 3.54%; N, 8.38%.

COOH

Example 5 coon Elementary analysis.Calculated (as C H O N C, 68.75%; H,3.13%; N, 7.29%. Found: C, 68.82%; H, 3.10; N, 7.33%.

Example 6 The same procedures as described in Example 3 were repeatedwith 2.16 parts of pyromellitic dianhydride, 3.06 parts of5,6-diamino-3-nicotinic acid, and parts of N- methyl-Z-pyrrolidone. Thereaction was carried out at 210 C. for 3 hours, then the resultingreaction product was poured into a 50:50 Water ethanol solution and the3,474,109 7 8 precipitated product was separated and purified. Thisprod- 58.41%; H, 1.77%; N, 18.58%. Found: C, 58.65%; H, not was found tobe the imidazopyrrolone dicarboxylic 1.63%; N, 18.61%.

acid of the structural formula: Examples 740;

O O L 5 Employing the same procedures as described in Example 1. Thefollowing tricarboxylic anhydrides and tetra- HOOG N=C C=N COOH aminesas shown in Table 1 were reacted with each other,

and four kinds of imidazopyrrolone dicarboxylic acids as Elementaryanalysis-Calculated (as C H O N C, shown in Table 2 were obtained,respectively.

TABLE 1 Amounts Amounts Tricarboxylic auhydride (parts) Tetraamme(parts) Example No.2

7 Ethylene tricarboxylic anhydride l,2,4,5-tetraammo-beuzene 8 do3,3,4,4-tetraaminodiphenyl sulfidc coco $3590003,4,4-diphenyltricarboxylic anhydr 3,3,4,4-tetraaminodiphenyl ketone.Trimcllitic anhydride 1,2,4,5-tetraaim'nob enzene TAB LE 2 Product(Structural formula) Example No.2

7 HOOC-CHZCH\ CHCHZCOOH Elementary analysis: Calculated (as CmHmOaNO! C,54.24%; H, 2.82%; N, 15.82%. Found: C, 54.44%; H, 2.77%; N, 15.86%.

C=N N=C 8 HOOC-CH CH l OHCH OOOH s C-N N-C 11 t Elementary analysis:Calculated (as CzzHuOaNtSOi 57- 2- Found: 7 N 1 Elementary analysis:Calculated (as C4aH2201N4): C, 73.08%; H, 3.12%; N, 7.93%. Found: C,73.26:% H, 3.06%; N, 7.95%.

Elementary analysis: Calculated (as 0241110 014) -44%. Found: C, 64-12.46%-

Examples 1 1-13 Employing the same procedures as described in Example 4,the following tricarboxylic anhydrides and diamino mono-carboxylic acidsas shown in Table 3 were 65 reacted to obtain the imidazopyrrolonedicarboxylic acids as shown in Table 4, respectively.

TABLE 3 Example Amounts Amounts N0. Tricarboxylic anhydridc (parts)Diauiiuo-rnonocarboxylic acid (parts) 11 Ethylene tricarboxylicanhydride 1. 44 3,4-diamiuo benzoic acid 1. 52 12 Trimcllitlc auhydride1.92 2,3-diamino-p-toluylic acid 1. 66 1'; do 1. 924,5-diamin0-2-naphthoic ac 2.02

TABLE 4 Product (Structural formula) Product (Structural formula)Example No.1 5 Example N0.

OOOH 13 I-IOOC-OHr-CH H000 COOH -C 0 u 0 Elementary analysis: Calculated(as C H O N 0, 55.387; H 3.087 Elementary analysis! Calculated 20 10 2):C. 67-04 H N, 10.77%. Found: 0, 55.61%:2H? 355%; N, 10.79%. N, 7.82%.Found: 0, 67.27%; H, 2.73%; N, 7.82%.

HO0C i Examples 14-20 f-" Employing the same procedures as described inEx- 0 am 1e 6 the followin tetra-carbox lic dianh drides and 5 O OH p gy 7 Elementary analysis: Calculated (as C11HmO5N2): C, 63.35%; H, 3.11%

N, 8.70%. Found: C, 63.36%; H, 3.07%; N, 8.71%.

aclds shown In Table 6, respectively.

diamino-monocarboxylic acids as shown in Table 5 were reacted to theobtain the imidazopyrrolone dicarboxylic TABLE 5 Example Amounts AmountsN0. Tetra-carboxylic dianhydride (parts) Diamino-mono-carboxylic acid(parts) 14 3,3,4,4-ben2ophenone tetracarboxyllc dianhydrlde 3. 223,4-diaminobezoic acid 3. 04 15 2,3,6,7-naphthalene tetracarboxylicdianhyclride 2. 24 2,3-diamino-p-t0lnylic acid. 3. 3 2

3,3,4,4-diphenylmethane tetraearboxylic dianh Ethylene tetracarboxyliedianhydride 1,2,3a4-cyclopentane tetracarboxylic dia y de 3.08 do 1. 703,4-diaminobenzoic acid 2.46 do 2. 46 4,5-diamino-2-napl1thoie acid 2.463,4-diaminohydroeinnamic acid TAB LE 6 Product (structural formula)Example N0.:

14- H O 0 C- Elementary analysis: Calculated (as C31H1407N4): 1%,67.15%; H, 2.53%; N, 10.11%.

Found: C, 67.28%; H, 2.50%; 10.15%.

15 C O OH Elementary analysis: Calculated (as C H O5N4): C, 68.18%; H,3.03%; N, 10.61%. Found: C, 68.33%; H, 3.01%; N, 10.64%.

16 ('30 OH C O OH N=C CHz- 3 3 CH3 CH3 Elementary analysis: Calculated(as C 3H2o0@N4): C, 69.72%; H, 3.52%; N, 9.86%. Found: C, 69.90%; H,3.34%; N, 9.88%.

N=C C=N 17 00 0- OOOH /CHCH NC C-N C Found: C, 59.91%; H, 2.45%; N,13.99%

TABLE 6.Coutinued Product (structural formula) Example No.: v

18 HOOC- N7C|C COOH ll ll Elementary analysis: Calculated (as CnHnOa O N12.07%- Found: C, 62.66%; H, 3.12%; N, 12.70%.

ll ll Elementary analysis: Calculated (as C HmOaNQ: C, 68.63%; H, 3.32%;N, 10.33%. Found: C, 68.83%; H, 3.12%; N, 10.37%.

20 HO0C-CHrCHz N7C C N "'CHZCHg-COOH iUi 0 6 Elementary analysis:Calculated (as C27H22O5N4 1 C, 65.06%; H, 4.42%; N, 11.24%.

Found: C, 65.20%; H, 4.40%; N, 11.28%.

Infrared spectra of the imidazopyrrolone dicarboxylic I Example 22 reacids obtamed in accordance with Examples 4 to 20 we 30 110 grams ofethylene g1 ycol, 75 grams of glycerol measured. As a result, in everycase of the above measurements, absorption band of 2000-8000 cm.- bycarboxyl group, those of 1765, 1720 and 720 cm." by carboxyl group,those of 1620 and 1565 cm.- by C=N group and that of 1360 cm.- by C--Ngroup were remarkably observed. While no absorption band of 1780 cm. byimide group and those of 1650, 1540 and 1280 cm? by amide group wereobserved. Furthermore, each melting point of the respectiveimidazopyrrolone dicarboxylic acids were found to be above 360 C.

For the purpose of illustrating the usefulness of the presentimidazopyrrolone dicarboxylic acids, polyester resins were prepared byemploying the present dicarboxylic acids and thus prepared resins werecoated on wires.

Example 21 Polyester was prepared according to a known method by using400 grams of dimethyl terephthalate, 110 grams and 200 grams ofimidazopyrrolone dicarboxylic acid obtained in Example 2 were reacted at200 C. for 5 hours. To this, 400 grams of dimethyl terephthalate wereadded, and the mixture was reacted at 170 C. for 5 hours andsubsequently at 240 C, for 5 hours.

Thus reacted mixturewas diluted with 450 grams of commercial cresol, andfurther added with a solution of 9 grams butyl titanate in 27 gramscommercial cresol and with a mixed solvent of 2 parts solvent naphthaand 1 part commercial cresol to prepare an enamel varnish.

When the varnish was applied on an annealed copper wire (diameter 1.0mm.) as in Example 21, a good quality enamel insulated wire with animproved heat resistance, impact strength and abrasion resistance wasobtained.

We claim:

1. An imidazopyrrolone dicarboxylic acid having the formula:

of ethylene glycol and 75 grams of glycerol. To this polyester, 140grams of imidazopyrrolone dicarboxylic H000 R R R'-CQ()H acid obtainedby the method of Example 1 were added,

and the mixture was stirred and heated at 180 C, When the addedimidazopyrrolone dicarboxylic acid was completely dissolved in thepolyester, 1.8 grams of cadmium acetate were added, and the mixture washeated up to 220 C. and reacted for 3 hours, under vacuum, at the sametemperature. Thus prepared polyester resin was diluted with 450 grams ofcommercial cresol and the solution was further added with a solution of9 grams butyl titanate in 27 grams commercial cresol. Thereafter, amixed solvent of 1 part solvent naphtha and 2 parts commercial cresolwas added thereto adjust the solid content in the solution to 35% of thetotal weight.

Thus prepared enamel varnish was coated on an annealed copper wire(diameter 1.0 mm.) and baked under the conditions of baking rate 7m./minute and baking temperature 470 C. This procedure was repeated 6times on the same copper wire, thereby obtained an enamel insulated wirehaving an insulating thin film (0.05 mm. in thickness) thereon. When theinsulated wire was compared with a conventional polyester enamelinsulated wire, it was found that the former possessed a far improvedheat resistance, impact strength, and abrasion resistance as comparedwith those of the latter.

wherein R is a tetravalent radical of the group con sisting of whereinthe N atoms in each imidazopyrrolone nucleus are bonded to ortho carbonatoms of R and wherein the C atoms in each of said imidazopyrrolonenuclei are bonded to the same or ortho carbon atoms of R' 2. Animidazopyrrolone dicarboxylic acid having the structural formula:

Boos-Q2? ZZQOOOH t l,

3. An imidazopyrrolone dicarboxylic acid having the formula:

OOOH

4. An irnidazopyrrolone dicarboxylic acid having the formula:

HO O G 0=N N=C- -00 OH CB Q6 10 ll 5. An imidazopyrrolone dicarboxylicacid having the formula:

6. An imidazopyrrolone dicarboxylic acid having the formula:

7. An irnidazopyrrolone dicarboxylic acid having the formula:

8. An imidazopyrrolone dicarboxylic acid having the formula:

9. A process for producing an imidazopyrrolone dicarboxylic acid as setforth in claim 1, which comprises heating approximately one mole of atetramine having the formula:

N NH HgN NHg wherein R is a member of the group consisting of I (I QQ inwhich X is CH S, O or CO, with approximately two moles of atricarboxylic acid anhydride having the formula:

CO HOOCR 0 wherein R' is a member of the group consisting of WQW s cCHzifH H Hz wherein R is a member of the group consisting of and inwhich X is CH S, O or CO, with approximately two 15 16 moles of atricarboxylic acid anhydride having the forture of said solvent toeffect condensation and intramolecmula: ular condensation.

H References Cited 000- 5 UNITED STATES PATENTS 2,884,423 4/1959Wilkinson 260256.4 wherein R 1s a member of the group cons1st1ng of2,949,467 8/1960 Staeublc 260 256 4 I I FOREIGN PATENTS r( W 1 101,189,218 3/1965 Germany.

d ALEX MAZEL, Primary Examiner an R. J. GALLAGHER, Assistant ExaminerUS. Cl. X.R.

CH2(:1H 15 in an inorganic or organic solvent at the reflux tempera-117-232; 260-75, 251, 256.4, 295.5, 346.3, 518

